Common alder can be found along riversides, and in fens and wet woodlands. Its exposed roots provide shelter for fish, and its rounded leaves are food for aquatic insects.

Largely confined to the north of the UK, the rare pine marten is mostly nocturnal and very hard to spot. Reintroductions are helping it make a comeback.

An uncommon tree of wet woodlands, riverbanks and heathlands, alder buckthorn displays pale green flowers in spring, and red berries that turn purple in autumn.

The tiny, brown-and-white sand martin is a common summer visitor to the UK, nesting in colonies on rivers, lakes and flooded gravel pits. It returns to Africa in winter.